1. Field of the Invention
Aspects of the present invention are directed to a servo write head design and, more particularly, to a servo write head design for writing servo patterns on magnetic tape.
2. Description of the Background
In tape drive systems that adopt timing-based servo (TBS) control, recorded servo patterns consist of transitions with two different azimuthal slopes. Servo reader head position (e.g., y-position or a y-estimate thereof) is derived from the relative timing of pulses generated by a servo reader or, in some cases, two or more servo readers. The servo reader(s) reads the servo patterns during read/write operations of the tape drive systems. TBS patterns also allow for the encoding of longitudinal position (LPOS) information without affecting the generation of the transversal position error signal (PES).
The servo patterns may be positioned in multiple servo bands, as specified in the linear tape-open (LTO) format, an example of which is shown in FIG. 1. The complete format for LTO drives of generation 1 (LTO-1) was standardized by the European Computer Manufacturers Association (ECMA) in 2001 as ECMA-319. Additional information on LTO technology, such as particular information on LTO drives of generations 2 to 4 (LTO-2 to LTO-4), where the servo format was not modified, can be readily found on the Internet.
As shown in FIG. 1, the servo patterns written by servo writer heads may be organized into 5 servo bands or, alternately, other numbers of servo bands. Where the servo patterns are organized into 5 servo bands, each servo band may have a servo band pitch of 2,859 μm and a servo band width of 186 μm. Data is stored in regions of the magnetic tape disposed in between the servo bands. Writing/reading of the information to/from the data tracks on the magnetic tape is performed by the data writers and readers that are located in the read-write head. In addition, the relative position of servo patterns in two adjacent servo bands in the longitudinal direction is defined by the LTO standard, which specifies a relative displacement of 33.33 or 66.66 μm, with a tolerance of +/−4.16 μm, between adjacent servo bands. The specified relative displacement of the servo patterns in different servo bands is introduced to allow for the rapid identification of the servo bands.
In all tape drive products, track-following and reel-to-reel servomechanisms rely on the generation of y-estimates and velocity estimates that describe a velocity of the tape and a position of a servo reader, which is also located in the read-write head, that generates signals from which the y-estimates and the velocity estimates are obtained. Thus, for proper operation of the servo control systems, a relatively high and relatively highly uniform rate of y-estimate generation, PES generation and velocity estimate generation is of great importance in determining a bandwidth of the servo systems. In conventional tape drive products, however, the uniform rate of y-estimate generation, PES generation and velocity estimate generation is limited to two estimates every servo frame.